237 lines
9.1 KiB
Plaintext
237 lines
9.1 KiB
Plaintext
Power Capping Framework
|
||
==================================
|
||
|
||
The power capping framework provides a consistent interface between the kernel
|
||
and the user space that allows power capping drivers to expose the settings to
|
||
user space in a uniform way.
|
||
|
||
Terminology
|
||
=========================
|
||
The framework exposes power capping devices to user space via sysfs in the
|
||
form of a tree of objects. The objects at the root level of the tree represent
|
||
'control types', which correspond to different methods of power capping. For
|
||
example, the intel-rapl control type represents the Intel "Running Average
|
||
Power Limit" (RAPL) technology, whereas the 'idle-injection' control type
|
||
corresponds to the use of idle injection for controlling power.
|
||
|
||
Power zones represent different parts of the system, which can be controlled and
|
||
monitored using the power capping method determined by the control type the
|
||
given zone belongs to. They each contain attributes for monitoring power, as
|
||
well as controls represented in the form of power constraints. If the parts of
|
||
the system represented by different power zones are hierarchical (that is, one
|
||
bigger part consists of multiple smaller parts that each have their own power
|
||
controls), those power zones may also be organized in a hierarchy with one
|
||
parent power zone containing multiple subzones and so on to reflect the power
|
||
control topology of the system. In that case, it is possible to apply power
|
||
capping to a set of devices together using the parent power zone and if more
|
||
fine grained control is required, it can be applied through the subzones.
|
||
|
||
|
||
Example sysfs interface tree:
|
||
|
||
/sys/devices/virtual/powercap
|
||
??? intel-rapl
|
||
??? intel-rapl:0
|
||
? ??? constraint_0_name
|
||
? ??? constraint_0_power_limit_uw
|
||
? ??? constraint_0_time_window_us
|
||
? ??? constraint_1_name
|
||
? ??? constraint_1_power_limit_uw
|
||
? ??? constraint_1_time_window_us
|
||
? ??? device -> ../../intel-rapl
|
||
? ??? energy_uj
|
||
? ??? intel-rapl:0:0
|
||
? ? ??? constraint_0_name
|
||
? ? ??? constraint_0_power_limit_uw
|
||
? ? ??? constraint_0_time_window_us
|
||
? ? ??? constraint_1_name
|
||
? ? ??? constraint_1_power_limit_uw
|
||
? ? ??? constraint_1_time_window_us
|
||
? ? ??? device -> ../../intel-rapl:0
|
||
? ? ??? energy_uj
|
||
? ? ??? max_energy_range_uj
|
||
? ? ??? name
|
||
? ? ??? enabled
|
||
? ? ??? power
|
||
? ? ? ??? async
|
||
? ? ? []
|
||
? ? ??? subsystem -> ../../../../../../class/power_cap
|
||
? ? ??? uevent
|
||
? ??? intel-rapl:0:1
|
||
? ? ??? constraint_0_name
|
||
? ? ??? constraint_0_power_limit_uw
|
||
? ? ??? constraint_0_time_window_us
|
||
? ? ??? constraint_1_name
|
||
? ? ??? constraint_1_power_limit_uw
|
||
? ? ??? constraint_1_time_window_us
|
||
? ? ??? device -> ../../intel-rapl:0
|
||
? ? ??? energy_uj
|
||
? ? ??? max_energy_range_uj
|
||
? ? ??? name
|
||
? ? ??? enabled
|
||
? ? ??? power
|
||
? ? ? ??? async
|
||
? ? ? []
|
||
? ? ??? subsystem -> ../../../../../../class/power_cap
|
||
? ? ??? uevent
|
||
? ??? max_energy_range_uj
|
||
? ??? max_power_range_uw
|
||
? ??? name
|
||
? ??? enabled
|
||
? ??? power
|
||
? ? ??? async
|
||
? ? []
|
||
? ??? subsystem -> ../../../../../class/power_cap
|
||
? ??? enabled
|
||
? ??? uevent
|
||
??? intel-rapl:1
|
||
? ??? constraint_0_name
|
||
? ??? constraint_0_power_limit_uw
|
||
? ??? constraint_0_time_window_us
|
||
? ??? constraint_1_name
|
||
? ??? constraint_1_power_limit_uw
|
||
? ??? constraint_1_time_window_us
|
||
? ??? device -> ../../intel-rapl
|
||
? ??? energy_uj
|
||
? ??? intel-rapl:1:0
|
||
? ? ??? constraint_0_name
|
||
? ? ??? constraint_0_power_limit_uw
|
||
? ? ??? constraint_0_time_window_us
|
||
? ? ??? constraint_1_name
|
||
? ? ??? constraint_1_power_limit_uw
|
||
? ? ??? constraint_1_time_window_us
|
||
? ? ??? device -> ../../intel-rapl:1
|
||
? ? ??? energy_uj
|
||
? ? ??? max_energy_range_uj
|
||
? ? ??? name
|
||
? ? ??? enabled
|
||
? ? ??? power
|
||
? ? ? ??? async
|
||
? ? ? []
|
||
? ? ??? subsystem -> ../../../../../../class/power_cap
|
||
? ? ??? uevent
|
||
? ??? intel-rapl:1:1
|
||
? ? ??? constraint_0_name
|
||
? ? ??? constraint_0_power_limit_uw
|
||
? ? ??? constraint_0_time_window_us
|
||
? ? ??? constraint_1_name
|
||
? ? ??? constraint_1_power_limit_uw
|
||
? ? ??? constraint_1_time_window_us
|
||
? ? ??? device -> ../../intel-rapl:1
|
||
? ? ??? energy_uj
|
||
? ? ??? max_energy_range_uj
|
||
? ? ??? name
|
||
? ? ??? enabled
|
||
? ? ??? power
|
||
? ? ? ??? async
|
||
? ? ? []
|
||
? ? ??? subsystem -> ../../../../../../class/power_cap
|
||
? ? ??? uevent
|
||
? ??? max_energy_range_uj
|
||
? ??? max_power_range_uw
|
||
? ??? name
|
||
? ??? enabled
|
||
? ??? power
|
||
? ? ??? async
|
||
? ? []
|
||
? ??? subsystem -> ../../../../../class/power_cap
|
||
? ??? uevent
|
||
??? power
|
||
? ??? async
|
||
? []
|
||
??? subsystem -> ../../../../class/power_cap
|
||
??? enabled
|
||
??? uevent
|
||
|
||
The above example illustrates a case in which the Intel RAPL technology,
|
||
available in Intel® IA-64 and IA-32 Processor Architectures, is used. There is one
|
||
control type called intel-rapl which contains two power zones, intel-rapl:0 and
|
||
intel-rapl:1, representing CPU packages. Each of these power zones contains
|
||
two subzones, intel-rapl:j:0 and intel-rapl:j:1 (j = 0, 1), representing the
|
||
"core" and the "uncore" parts of the given CPU package, respectively. All of
|
||
the zones and subzones contain energy monitoring attributes (energy_uj,
|
||
max_energy_range_uj) and constraint attributes (constraint_*) allowing controls
|
||
to be applied (the constraints in the 'package' power zones apply to the whole
|
||
CPU packages and the subzone constraints only apply to the respective parts of
|
||
the given package individually). Since Intel RAPL doesn't provide instantaneous
|
||
power value, there is no power_uw attribute.
|
||
|
||
In addition to that, each power zone contains a name attribute, allowing the
|
||
part of the system represented by that zone to be identified.
|
||
For example:
|
||
|
||
cat /sys/class/power_cap/intel-rapl/intel-rapl:0/name
|
||
package-0
|
||
|
||
The Intel RAPL technology allows two constraints, short term and long term,
|
||
with two different time windows to be applied to each power zone. Thus for
|
||
each zone there are 2 attributes representing the constraint names, 2 power
|
||
limits and 2 attributes representing the sizes of the time windows. Such that,
|
||
constraint_j_* attributes correspond to the jth constraint (j = 0,1).
|
||
|
||
For example:
|
||
constraint_0_name
|
||
constraint_0_power_limit_uw
|
||
constraint_0_time_window_us
|
||
constraint_1_name
|
||
constraint_1_power_limit_uw
|
||
constraint_1_time_window_us
|
||
|
||
Power Zone Attributes
|
||
=================================
|
||
Monitoring attributes
|
||
----------------------
|
||
|
||
energy_uj (rw): Current energy counter in micro joules. Write "0" to reset.
|
||
If the counter can not be reset, then this attribute is read only.
|
||
|
||
max_energy_range_uj (ro): Range of the above energy counter in micro-joules.
|
||
|
||
power_uw (ro): Current power in micro watts.
|
||
|
||
max_power_range_uw (ro): Range of the above power value in micro-watts.
|
||
|
||
name (ro): Name of this power zone.
|
||
|
||
It is possible that some domains have both power ranges and energy counter ranges;
|
||
however, only one is mandatory.
|
||
|
||
Constraints
|
||
----------------
|
||
constraint_X_power_limit_uw (rw): Power limit in micro watts, which should be
|
||
applicable for the time window specified by "constraint_X_time_window_us".
|
||
|
||
constraint_X_time_window_us (rw): Time window in micro seconds.
|
||
|
||
constraint_X_name (ro): An optional name of the constraint
|
||
|
||
constraint_X_max_power_uw(ro): Maximum allowed power in micro watts.
|
||
|
||
constraint_X_min_power_uw(ro): Minimum allowed power in micro watts.
|
||
|
||
constraint_X_max_time_window_us(ro): Maximum allowed time window in micro seconds.
|
||
|
||
constraint_X_min_time_window_us(ro): Minimum allowed time window in micro seconds.
|
||
|
||
Except power_limit_uw and time_window_us other fields are optional.
|
||
|
||
Common zone and control type attributes
|
||
----------------------------------------
|
||
enabled (rw): Enable/Disable controls at zone level or for all zones using
|
||
a control type.
|
||
|
||
Power Cap Client Driver Interface
|
||
==================================
|
||
The API summary:
|
||
|
||
Call powercap_register_control_type() to register control type object.
|
||
Call powercap_register_zone() to register a power zone (under a given
|
||
control type), either as a top-level power zone or as a subzone of another
|
||
power zone registered earlier.
|
||
The number of constraints in a power zone and the corresponding callbacks have
|
||
to be defined prior to calling powercap_register_zone() to register that zone.
|
||
|
||
To Free a power zone call powercap_unregister_zone().
|
||
To free a control type object call powercap_unregister_control_type().
|
||
Detailed API can be generated using kernel-doc on include/linux/powercap.h.
|